Multi-material 3D printed hydraulic actuator for medical robots

Abstract

<jats:sec> <jats:title content-type="abstract-subheading">Purpose</jats:title> <jats:p>This study aims to investigate the potential of using polymer multi-material additive manufacturing (MMAM) to produce miniature hydraulic piston actuators combining rigid structures and flexible seals. Such actuators offer great potential for medical robots in X-ray and magnetic resonance environments, where conventional piston actuators cannot be used because of safety issues caused by metal components.</jats:p> </jats:sec> <jats:sec> <jats:title content-type="abstract-subheading">Design/methodology/approach</jats:title> <jats:p>Hydraulic pistons with two different integrated flexible seal shapes are designed and manufactured using MMAM. Design 1 features a ring-shaped seal made from a flexible material that is printed on the surface of the rigid piston shaft. Design 2 appears identical from the outside, yet an axial opening in the piston shaft is added to enable self-reinforced sealing as fluid pressure increases. For both designs, samples with three different outer diameters are fabricated leading to a total of six different piston versions. The pistons are then evaluated regarding leakage, friction and durability.</jats:p> </jats:sec> <jats:sec> <jats:title content-type="abstract-subheading">Findings</jats:title> <jats:p>Measurement results show that the friction force for Design 2 is lower than that of Design 1, making Design 2 more suitable for the intended application. None of the versions of Design 2 shows leakage for pressures up to 1.5 MPa. For Design 1, leak-tightness varies with the outer diameter, yet none of the versions is consistently leak-tight at 1.5 MPa. Furthermore, the results show that prolonged exposure to water decreases the durability of the flexible material significantly. The durability the authors observe may, however, be sufficient for short-term or single-use devices.</jats:p> </jats:sec> <jats:sec> <jats:title content-type="abstract-subheading">Originality/value</jats:title> <jats:p>The authors investigate a novel design approach for hydraulic piston actuators based on MMAM. These actuators are of particular interest for patient-specific medical devices used in radiological interventions, where metal-free components are required to safely operate in X-ray and magnetic resonance environments. This study may serve as a basis for the development of new actuators, as it shows a feasible solution, yet pointing out critical aspects such as the influence of small geometry changes or material performance changes caused by water absorption.</jats:p> </jats:sec>

Design and Experimental Characterization of Hydraulically Actuated Revolute Joint Based on Multimaterial Additive Manufacturing

“…The capacity to produce multimaterial components was exploited to design each piston as a single part, with a hollow shape at the tip. It was observed [18] this creates an adaptive sealing effect: friction between the piston and the bore is reduced for low fluid pressure, while high fluid pressure increases the friction to avoid leakage (Fig. ??).…”

“…There are still limits to the proposed hydraulic-based actuated joint in its current implementation. First, the use of Polyjet process as considered here with TangoBlack plus material was observed to suffer from material degradation for long-term uses [18]. Further process development would help to have functional systems with large endurance.…”

A Low-Cost Miniature Electrohydrostatic Actuator System

“…The valves are a very simple three-piece assembly with an assembled diameter of 3 mm. Multi material additive manufacturing has been used to print hydraulic actuators with integrated seals safe for medical applications [15]. These examples show how 3D printing is being utilized to produce very low-pressure hydraulic components in ways not possible by traditional manufacturing methods.…”

Design, additive manufacturing and component testing of pneumatic rotary vane actuators for lightweight robots

“…However, for direct AM of complex multi-material components, only a few technologies are available. The most wide-spread commercial option is the PolyJet (PJ) process (Siegfarth et al , 2020), in which objects of desired shapes are accumulated from droplets of acrylate-based photocurable ink that are deposited via piezo nozzles and cured by infrared light. Kundera and Bochnia (2014) fabricated O-ring seals using PJ technology and found that, although the seals were usable, they exhibited complex time-dependent mechanical behavior.…”